Abstract

Technological innovation in all areas has led to the appearance in recent years of new metallic and pearlescent materials, yet no exhaustive studies have been conducted to assess their colorimetric capabilities. The chromatic variability of these special-effect pigments may largely be due to the three-dimensional effect of their curved shapes and orientations when they are directionally or diffusely illuminated. Our study examines goniochromatic colors using the optimal colors (MacAdam limits) associated with normal colors (photometric scale of relative spectral reflectance from 0 to 1) under certain conventional illuminants and other light sources. From a database of 91 metallic and interference samples and using a multi-gonio-spectrophotometer, we analyzed samples with lightness values of more than 100 and others with lightness values of less than 100, but with higher chromaticities than optimal colors, which places them beyond the MacAdam limits. Our study thus demonstrates the existence of chromatic perceptions beyond the normal solid color associated with these materials and independent of the light source. The challenge for future research, therefore, is to replicate and render these color appearances in current and future color reproduction technologies for computer graphics.

Figures (10)

Illumination and observation angles of the measures of the Datacolor MultiFX10 gonio-spectrophotometer in accordance with the DIN 6175-2 and ASTM E2194 standards. Top: aspecular line; bottom: interference line.

Rösch–MacAdam color solid associated with the CIE 1931 standard observer and the D65 illuminant together with the 91 goniochromatic samples measured by the Datacolor FX10 multi-gonio-spectrophotometer for the 25°/170° and 25°/140° measurement geometries.

Rösch–MacAdam color solid associated with the CIE 1931 standard observer and the different light sources together with the 91 goniochromatic samples measured with Datacolor FX10 multi-gonio-spectrophotometer for the 45°/120° measurement geometry.